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Mirrors > Home > ILE Home > Th. List > difeq2 | GIF version |
Description: Equality theorem for class difference. (Contributed by NM, 10-Feb-1997.) (Proof shortened by Andrew Salmon, 26-Jun-2011.) |
Ref | Expression |
---|---|
difeq2 | ⊢ (𝐴 = 𝐵 → (𝐶 ∖ 𝐴) = (𝐶 ∖ 𝐵)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eleq2 2142 | . . . 4 ⊢ (𝐴 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵)) | |
2 | 1 | notbid 624 | . . 3 ⊢ (𝐴 = 𝐵 → (¬ 𝑥 ∈ 𝐴 ↔ ¬ 𝑥 ∈ 𝐵)) |
3 | 2 | rabbidv 2593 | . 2 ⊢ (𝐴 = 𝐵 → {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵}) |
4 | dfdif2 2981 | . 2 ⊢ (𝐶 ∖ 𝐴) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} | |
5 | dfdif2 2981 | . 2 ⊢ (𝐶 ∖ 𝐵) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵} | |
6 | 3, 4, 5 | 3eqtr4g 2138 | 1 ⊢ (𝐴 = 𝐵 → (𝐶 ∖ 𝐴) = (𝐶 ∖ 𝐵)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 = wceq 1284 ∈ wcel 1433 {crab 2352 ∖ cdif 2970 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-in1 576 ax-in2 577 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-11 1437 ax-4 1440 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 ax-ext 2063 |
This theorem depends on definitions: df-bi 115 df-tru 1287 df-nf 1390 df-sb 1686 df-clab 2068 df-cleq 2074 df-clel 2077 df-ral 2353 df-rab 2357 df-dif 2975 |
This theorem is referenced by: difeq12 3085 difeq2i 3087 difeq2d 3090 ssdifeq0 3325 2oconcl 6045 diffitest 6371 diffifi 6378 |
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